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Insights on efficacious doses of PAMORA s for patients on chronic opioid therapy or opioid‐naïve patients
Author(s) -
Malderen K.,
Halawi H.,
Camilleri M.
Publication year - 2018
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1111/nmo.13250
Subject(s) - naltrexone , opioid , medicine , (+) naloxone , opioid antagonist , chronic pain , opioid receptor , anesthesia , pharmacology , morphine , receptor , physical therapy
Background Opioid‐induced constipation ( OIC ) is a major side effect of opioid use. Centrally acting antagonists result in opioid withdrawal or worsening of pain and lead to use of peripherally acting mu‐opioid receptor antagonists ( PAMORA s). The required doses of the PAMORA s, methylnaltrexone and naloxegol, in the treatment of OIC are well established in chronic opioid users. OIC may occur after short duration of opioid treatment; the required doses of naloxone, naltrexone, and PAMORA s in opioid‐naïve subjects (with no opioid use for at least 3 months) are unclear. The aim of this review was to evaluate the PAMORA dose required for opioid‐naïve subjects to achieve similar beneficial effects on symptoms or valid surrogates to those observed in chronic opioid users. Methods A PubMed search of μ‐opioid antagonists to counter μ‐opioid effects included terms: naloxone, naltrexone, methylnaltrexone, alvimopan, and naloxegol, as well as OIC and colonic transit. Key Results The approved dose of methylnaltrexone in chronic opioid users, 0.3 mg/kg subcutaneous ( SQ ), did not affect motility in opioid‐naïve subjects. Trials investigating the required dose of alvimopan showed 0.5‐1 mg dose was efficacious in treating OIC ; a 10‐fold higher dose (12 mg) of alvimopan is needed to block effects of codeine on small bowel and colonic transit in opioid‐naïve subjects compared to chronic opioid users. Opioid‐naïve users need 125 mg of naloxegol to reverse the effects of opioids on transit; this is in contrast to the 12.5 to 25 mg needed to treat OIC in chronic opioid users. Conclusions & Inferences Opioid‐naïve subjects require a higher dose of PAMORA than chronic opioid users to achieve μ‐opioid antagonist effect.